We saw humans turn into the flightless wyrms... I don't think they are true dragons. There seems to be at least two species, the two legged, winged ones and the four legged winged ones. Granted, dragons being able to shapeshift to human forms is a staple of fantasy, but as of yet I don't think we've seen 'true' dragons do it. I'd love some more clarifiction on this if I missed it, as Ferne did say at fan fest we'd learn more about the shapechangers in this patch (during the interview with gamerescape).